1. Field of the Invention
The present invention relates to a zoom lens. The present invention further relates to an image pickup apparatus, such as a digital camera and video camera, equipped with a zoom lens and an image pickup element.
2. Description of the Related Art
In recent years, digital cameras have replaced film cameras to become the mainstream in the technical field of the image pickup apparatus. Digital cameras have image pickup areas that are generally smaller in size than those of film cameras, and therefore a reduction in the size of digital cameras can be achieved more easily. Nowadays, since there is the trend that a higher importance is placed on the portability as compared to the past, the sizes of digital cameras have been made smaller. Furthermore, since consumers wish to enjoy easy shooting in both indoor and outdoor shooting situations, increases in the angle of view and increases in the zoom ratio of zoom lenses used as the optical systems of digital cameras are needed.
Various zoom lenses have been developed in the past with a view to achieve a smallness in size, a wide angle of view, and a high zoom ratio. For example, Japanese Patent Application Laid-Open Nos. 2006-208889 and 11-84242 disclose negative-front type zoom lenses in which the lens unit located closest to the object side has a negative refracting power. The negative front type zoom lens like this has a retro-focus type overall refracting power arrangement, which is more advantageous in achieving a large angle of view at the wide angle end as compared to the positive-front type zoom lens, and also advantageous in achieving smallness in the overall size of the zoom lens by virtue of a reduction in the size of the lens unit closest to the object side.
The zoom lenses disclosed in Japanese Patent Application Laid-Open Nos. 2006-208889 and 11-84242, mentioned above byway of example, include, in order from the object side thereof, a first lens unit having a negative refracting power, a second lens unit having a positive refracting power, a third lens unit having a negative refracting power, and a fourth lens unit having a positive refracting power, wherein during zooming from the wide angle end to the telephoto end, the second lens unit and the third lens unit are moved toward the object side.